Low Cost High Quality Fabrication Methods and CAD for Diffractive Optics and Computer Holograms Compatible with Micro-Electronics and Micro-Mechanics Fabrication

Abstract

State-of-the-art diffractive optical elements (DOEs) and computer generated holograms (CGHs) are fabricated using e-beam lithography and dry etching techniques to achieve multi-level phase elements with very high diffraction efficiencies. Electron beam lithography allows DOEs/CGHs with smaller feature sizes (e.g. for off-axis diffractive lenses with small f-number) to be fabricated. Dry etching techniques, especially chemically assisted reactive ion beam, allows DOEs/CGHs be fabricated in a variety of materials. Multi-level phase DOEs/CGHs, especially those of sixteen or more phase levels, mean their surface profiles are fabricated with high accuracy / quality. It is not only the e-beam system which dictates the feature size limitations, but also the alignment systems (mask aligner) and the materials (e-beam or photo resists). In order to allow DOEs/CGHs to be used in new optoelectronic systems, it is necessary also to fabricate the elements in different materials economically. Since the cost of a multi-level phase DOE/CGH is determined by the e-beam writing time, the number of etching steps for fabricating the master, and the technology for replication, we need to decrease the writing time and etching steps for the master and to develop a low cost replication technology for mass production without affecting the quality of the DOEs/CGHs. In this Chapter, we will review three DOE/CGH fabrication techniques and CAD development required, considering the overall design and fabrication time for multi-level phase DOEs.